Developmental studies on melanoma of the skin and mouth mucosa of dogs

Abstract

Progressive studies in dogs with skin and oral melanomas were undertaken to determine whether or not the WHO-classification of melanomas, which is based mainly on histological criteria, reflects sufficiently the biological behaviour of these tumours. Furthermore, some prognostic parameters, important in the prognosis of human malignant melanomas were tested with respect to their significance for canine melanomas. The paper deals with progressive studies in 182 dogs with surgically treated benign and malignant skin and oral melanomas. Parameters of the biological behaviour were the 2 years death rate and the median survival time. The melanomas were classified according to the recommendations of the WHO. Within 2 years after the first treatment five (5.7%) of 87 dogs with benign skin melanomas, 29 (65.9%) of 44 dogs with malignant skin melanomas and 44 (86.2%) of 55 dogs with malignant oral melanomas were killed because of recurrence or metastases or both. The median survival time of dogs with benign skin melanomas was more than 24 months, with malignant skin melanomas 8 months and with malignant oral melanomas 3 months. In dogs with large malignant skin melanomas the 2 years death rate was 100% with a median survival time of 4 months, whereas animals with small melanomas had a 2 years death rate of 54.3% and a median survival time of 12 months. The site of skin melanomas, sex and histological type of both skin and oral melanomas, however, had no significant influence on the course of the disease. Also, histological parameters, important in the prognosis of human malignant melanoma (rate of mitosis, size of nucleoli, pigmentation and vascular invasion), had no significant influence on the course of the disease.